Thermally modified oxide based pretreatments for metals and methods of making the same

ABSTRACT

Provided herein are corrosion resistant metal substrates and methods for producing the same by thermal modification. The disclosure provides methods for producing corrosion resistant substrates by producing a pretreatment film on a surface of a metal substrate and heating the pretreated metal substrate. In particular, the metal substrate and/or the pretreated metal substrate of these methods is in an F temper, a T4 temper, or a T6 temper.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to and filing benefit of U.S.provisional patent application Ser. No. 63/015,056, filed Apr. 24, 2020,which is incorporated herein by reference in its entirety.

FIELD

The present disclosure generally relates to processing of metalsubstrates, such as aluminum alloys. More specifically, the presentdisclosure relates to thermal modification of pretreated metalsubstrates.

BACKGROUND

Certain metal products, such as aluminum alloys, can benefit frompretreatment, e.g., the application or production of a pretreatment filmon a surface of the metal product. These benefits include bonddurability, color stability, ease of maintenance, aesthetics, health andsafety, and low cost. However, it is difficult to produce aluminum alloycoils having a pretreatment film that meets flexibility, durabilityand/or surface characteristics requirements for downstream processing,including joining of aluminum alloy products. Furthermore, conventionalmethods require limiting the exposure of the pretreated metal to hightemperatures, e.g., to avoid loss of the above-described benefits. Thislimits the types of products, e.g., the tempers of the aluminum alloys,that may be pretreated.

SUMMARY

Covered embodiments of the invention are defined by the claims, not thissummary. This summary is a high-level overview of various aspects of theinvention and introduces some of the concepts that are further describedin the Detailed Description section below. This summary is not intendedto identify key or essential features of the claimed subject matter, noris it intended to be used in isolation to determine the scope of theclaimed subject matter. The subject matter should be understood byreference to appropriate portions of the entire specification, any orall drawings, and each claim.

In one aspect, the present disclosure describes a method of making acorrosion resistant substrate, the method comprising producing apretreatment film on a surface of a metal substrate to provide apretreated metal substrate; and heating the pretreated metal substrateat a first temperature to provide the corrosion resistant substrate,wherein the first temperature is greater than 300° C.; and wherein themetal substrate and/or the pretreated metal substrate is in an F temper,a T4 temper, or a T6 temper. In some cases, the metal substratecomprises an aluminum alloy (e.g., a 5xxx series aluminum alloy, a 6xxxseries aluminum alloy, or a 7xxx series aluminum alloy). In some cases,the corrosion resistant substrate is in a T6 temper. In some cases, thepretreatment film comprises an oxide layer. In some cases, the oxidelayer comprises an aluminum oxide, a silicon oxide, a titanium oxide, achromium oxide, a manganese oxide, a nickel oxide, a yttrium oxide, azirconium oxide, a molybdenum oxide, or combinations thereof. In somecases, producing the pretreatment film comprises applying an inorganicpretreatment composition to the surface of the metal substrate. In somecases, producing the pretreatment film comprises anodizing the surfaceof the metal substrate. In some cases, producing the pretreatment filmcomprises flame hydrolyzing the surface of the metal substrate. In somecases, the first temperature is from 300° C. to 550° C. In some cases,the heating comprises heating the pretreated metal substrate at thefirst temperature for less than 30 minutes. Optionally, the heatingfurther comprises heating the pretreated metal substrate at a secondtemperature. In some cases, the second temperature is lower than thefirst temperature. In some cases, the second temperature is from 75° C.to 250° C. In some cases, the heating comprises heating the pretreatedmetal substrate at the second temperature from 1 hour to 48 hours. Insome cases, the metal substrate is a continuous coil.

In another aspect, the present disclosure describes a corrosionresistant coil comprising an aluminum alloy continuous coil, wherein asurface of the aluminum alloy continuous coil comprises an inorganicpretreatment film, and wherein the aluminum alloy continuous coil is inan F temper, a T4 temper, or a T6 temper. In some cases, the aluminumalloy continuous coil comprises a 5xxx series aluminum alloy, a 6xxxseries aluminum alloy, or a 7xxx series aluminum alloy. In some cases,the inorganic pretreatment film comprises an oxide layer. In some cases,the oxide layer comprises an aluminum oxide, a silicon oxide, a titaniumoxide, a chromium oxide, a manganese oxide, a nickel oxide, a yttriumoxide, a zirconium oxide, a molybdenum oxide, or combinations thereof.

In another aspect, the present disclosure describes a method of making acorrosion resistant substrate, the method comprising producing apretreatment film on a surface of a metal substrate to provide apretreated metal substrate; and heating the pretreated metal substrateat a first temperature to provide the corrosion resistant substrate,wherein the metal substrate and/or the pretreated metal substrate is inan F temper, and wherein the corrosion resistant substrate is in a T5temper, a T6 temper, a T61 temper, a T7 temper, T8x temper, or a T9temper.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is described in detail below with reference to theappended drawings.

FIG. 1 illustrate results from glow discharge optical emissionspectrometry (GDOES) analysis of corrosion resistant substratesaccording to certain aspects of the present disclosure.

DETAILED DESCRIPTION

Described herein are methods for making a corrosion resistant metalsubstrate, such as a corrosion resistant aluminum alloy substrate. Thecorrosion resistant substrates described herein can be used, forexample, to produce corrosion resistant products that have superiorsurface qualities and minimized surface defects as compared to productsprepared from metal substrates that have not been processed according tothe present disclosure.

Various pretreatments are often employed in conventional processing ofmetal substrates, such as aluminum alloys. Some conventional processesproduce a pretreatment film on one or more surfaces of the metalsubstrate by chemical or electrolytic modification. The pretreatmentfilm may alter properties of the metal substrate, such as bonddurability, adhesion, or corrosion rate. In conventional methods, themetal substrates are not subjected to thermal modification afterpretreatment. In particular, conventional methods avoid exposingpretreatment films on surfaces of metal substrates to high temperatures(e.g., temperatures greater than 400° C.). For example, conventionalmethods dry pretreated surfaces at temperatures less than 100° C. Thisis due to the commonly held belief by those of ordinary skill in the artthat exposure to high temperatures would degrade the pretreatment film,e.g., by burning the pretreatment film, or otherwise reducing theeffectiveness of the pretreatment film. Furthermore, because of thecommonly held belief that exposure to high temperatures provides noadvantage, thermal modification of metal substrates after pretreatmentwas considered to be an unnecessary additional cost to be avoided.

Despite the conventional belief urging otherwise, the methods describedherein include intentionally exposing pretreatment films to hightemperatures. The present disclosure provides methods of making acorrosion resistant metal substrate by producing a pretreatment film ona surface of a metal substrate and heating the pretreated metalsubstrate to a temperature greater than 400° C. The exposure ofpretreatment films to high temperatures (e.g., greater than 400° C.)according to the methods described herein do not degrade or negativelyimpact the pretreatment film. On the contrary, the high temperaturesimprove (e.g., enhance) the properties of the pretreatment film. Heatingthe pretreated metal substrate according to the present disclosure driesand/or densifies the pretreatment film, improving the bond durability,adhesion, and/or corrosion resistance imparted by the pretreatment film.

Thus, the corrosion resistant substrates produced by the methodsdescribed herein exhibit excellent physical properties, such as bonddurability. Furthermore, the processes described herein are suitable forcoil-to-coil lines as well as batch processing.

Definitions and Descriptions

As used herein, the terms “invention,” “the invention,” “this invention”and “the present invention” are intended to refer broadly to all of thesubject matter of this patent application and the claims below.Statements containing these terms should be understood not to limit thesubject matter described herein or to limit the meaning or scope of thepatent claims below.

In this description, reference is made to alloys identified by aluminumindustry designations, such as “series” or “7xxx.” For an understandingof the number designation system most commonly used in naming andidentifying aluminum and its alloys, see “International AlloyDesignations and Chemical Composition Limits for Wrought Aluminum andWrought Aluminum Alloys” or “Registration Record of Aluminum AssociationAlloy Designations and Chemical Compositions Limits for Aluminum Alloysin the Form of Castings and Ingot,” both published by The AluminumAssociation.

As used herein, a plate generally has a thickness of greater than about15 mm. For example, a plate may refer to an aluminum product having athickness of greater than 15 mm, greater than 20 mm, greater than 25 mm,greater than 30 mm, greater than 35 mm, greater than 40 mm, greater than45 mm, greater than 50 mm, or greater than 100 mm.

As used herein, a shate (also referred to as a sheet plate) generallyhas a thickness of from about 4 mm to about 15 mm. For example, a shatemay have a thickness of 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11mm, 12 mm, 13 mm, 14 mm, or 15 mm.

As used herein, a sheet generally refers to an aluminum product having athickness of less than about 4 mm. For example, a sheet may have athickness of less than 4 mm, less than 3 mm, less than 2 mm, less than 1mm, less than 0.5 mm, less than 0.3 mm, or less than 0.1 mm.

As used herein, “bond durability” refers to an ability of a bondingagent bonding two products together to withstand cycled mechanicalstress after exposure to environmental conditions that initiate failureof the bonding agent. Bond durability is characterized in terms of thenumber of mechanical stress cycles applied to the bonded products, whilethe bonded products are exposed to the environmental conditions, untilthe bond fails.

As used herein, terms such as “cast metal product,” “cast product,”“cast aluminum alloy product,” and the like are interchangeable andrefer to a product produced by direct chill casting (including directchill co-casting) or semi-continuous casting, continuous casting(including, for example, by use of a twin belt caster, a twin rollcaster, a twin block caster, or any other continuous caster),electromagnetic casting, hot top casting, or any other casting method.

As used herein, a “coil-to-coil” line or “coil-to-coil processing”refers to a continuous processing method on a continuous line wherebythe alloy, e.g., aluminum alloy, processed in the method is fed into theprocessing from a coil, uncoiled during the processing, and re-coiledafter completing the processing. An alloy processed is such a processingmethod is referred to herein as a “continuous coil” or an “aluminumalloy continuous coil.”

Reference is made in this application to alloy condition or temper. Foran understanding of the alloy temper descriptions most commonly used,see “American National Standards (ANSI) H35 on Alloy and TemperDesignation Systems.” An F condition or temper refers to an aluminumalloy as fabricated. An O condition or temper refers to an aluminumalloy after annealing. A T1 condition or temper refers to an aluminumalloy cooled from hot working and naturally aged (e.g., at roomtemperature). A T2 condition or temper refers to an aluminum alloycooled from hot working, cold worked, and naturally aged. A T3 conditionor temper refers to an aluminum alloy solution heat treated, coldworked, and naturally aged. A T4 condition or temper refers to analuminum alloy solution heat treated and naturally aged. A T5 conditionor temper refers to an aluminum alloy cooled from hot working andartificially aged (at elevated temperatures). A T6 condition or temperrefers to an aluminum alloy solution heat treated and artificially aged.A T7 condition or temper refers to an aluminum alloy solution heattreated and artificially overaged. A T8x condition or temper refers toan aluminum alloy solution heat treated, cold worked, and artificiallyaged. A T9 condition or temper refers to an aluminum alloy solution heattreated, artificially aged, and cold worked.

As used herein, the meaning of “a,” “an,” or “the” includes singular andplural references unless the context clearly dictates otherwise.

As used herein, the modifier “about” is intended to include thedescribed term without the word “about” (e.g., “about 10” is intended toinclude “10”).

As used herein, the meaning of “room temperature” can include atemperature of from about 15° C. to about 30° C., for example about 15°C., about 16° C., about 17° C., about 18° C., about 19° C., about 20°C., about 21° C., about 22° C., about 23° C., about 24° C., about 25°C., about 26° C., about 27° C., about 28° C., about 29° C., or about 30°C.

All ranges disclosed herein are to be understood to encompass any andall subranges subsumed therein. For example, a stated range of “1 to 10”should be considered to include any and all subranges between (andinclusive of) the minimum value of 1 and the maximum value of 10; thatis, all subranges beginning with a minimum value of 1 or more, e.g. 1 to6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to 10.

Metal Substrate

As noted, the present disclosure provides methods for making a corrosionresistant metal substrate. More specifically, the methods describedherein produce a pretreatment film on the surface of a metal substrate.The composition of the metal substrate on which the pretreatment film isformed is not particularly limited. The pretreatment film can beapplied, for example, to any suitable aluminum alloy, such as acontinuous coil of an aluminum alloy. Suitable aluminum alloys include,for example, 1xxx series aluminum alloys, 2xxx series aluminum alloys,3xxx series aluminum alloys, 4xxx series aluminum alloys, 5xxx seriesaluminum alloys, 6xxx series aluminum alloys, 7xxx series aluminumalloys, and 8xxx series aluminum alloys.

By way of non-limiting example, exemplary 1xxx series aluminum alloysfor use as the metal substrate can include AA1100, AA1100A, AA1200,AA1200A, AA1300, AA1110, AA1120, AA1230, AA1230A, AA1235, AA1435,AA1145, AA1345, AA1445, AA1150, AA1350, AA1350A, AA1450, AA1370, AA1275,AA1185, AA1285, AA1385, AA1188, AA1190, AA1290, AA1193, AA1198, orAA1199. In some cases, the aluminum alloy is at least 99.9% purealuminum (e.g., at least 99.91%, at least 99.92%, at least 99.93%, atleast 99.94%, at least 99.95%, at least 99.96%, at least 99.97%, atleast 99.98%, or at least 99.99% pure aluminum).

Non-limiting exemplary 2xxx series aluminum alloys for use as the metalsubstrate can include AA2001, AA2002, AA2004, AA2005, AA2006, AA2007,AA2007A, AA2007B, AA2008, AA2009, AA2010, AA2011, AA2011A, AA2111,AA2111A, AA2111B, AA2012, AA2013, AA2014, AA2014A, AA2214, AA2015,AA2016, AA2017, AA2017A, AA2117, AA2018, AA2218, AA2618, AA2618A,AA2219, AA2319, AA2419, AA2519, AA2021, AA2022, AA2023, AA2024, AA2024A,AA2124, AA2224, AA2224A, AA2324, AA2424, AA2524, AA2624, AA2724, AA2824,AA2025, AA2026, AA2027, AA2028, AA2028A, AA2028B, AA2028C, AA2029,AA2030, AA2031, AA2032, AA2034, AA2036, AA2037, AA2038, AA2039, AA2139,AA2040, AA2041, AA2044, AA2045, AA2050, AA2055, AA2056, AA2060, AA2065,AA2070, AA2076, AA2090, AA2091, AA2094, AA2095, AA2195, AA2295, AA2196,AA2296, AA2097, AA2197, AA2297, AA2397, AA2098, AA2198, AA2099, orAA2199.

Non-limiting exemplary 3xxx series aluminum alloys for use as the metalsubstrate can include AA3002, AA3102, AA3003, AA3103, AA3103A, AA3103B,AA3203, AA3403, AA3004, AA3004A, AA3104, AA3204, AA3304, AA3005,AA3005A, AA3105, AA3105A, AA3105B, AA3007, AA3107, AA3207, AA3207A,AA3307, AA3009, AA3010, AA3110, AA3011, AA3012, AA3012A, AA3013, AA3014,AA3015, AA3016, AA3017, AA3019, AA3020, AA3021, AA3025, AA3026, AA3030,AA3130, or AA3065.

Non-limiting exemplary 4xxx series aluminum alloys for use as the metalsubstrate can include AA4004, AA4104, AA4006, AA4007, AA4008, AA4009,AA4010, AA4013, AA4014, AA4015, AA4015A, AA4115, AA4016, AA4017, AA4018,AA4019, AA4020, AA4021, AA4026, AA4032, AA4043, AA4043A, AA4143, AA4343,AA4643, AA4943, AA4044, AA4045, AA4145, AA4145A, AA4046, AA4047,AA4047A, or AA4147.

Non-limiting exemplary 5xxx series aluminum alloys for use as the metalsubstrate can include AA5182, AA5183, AA5005, AA5005A, AA5205, AA5305,AA5505, AA5605, AA5006, AA5106, AA5010, AA5110, AA5110A, AA5210, AA5310,AA5016, AA5017, AA5018, AA5018A, AA5019, AA5019A, AA5119, AA5119A,AA5021, AA5022, AA5023, AA5024, AA5026, AA5027, AA5028, AA5040, AA5140,AA5041, AA5042, AA5043, AA5049, AA5149, AA5249, AA5349, AA5449, AA5449A,AA5050, AA5050A, AA5050C, AA5150, AA5051, AA5051A, AA5151, AA5251,AA5251A, AA5351, AA5451, AA5052, AA5252, AA5352, AA5154, AA5154A,AA5154B, AA5154C, AA5254, AA5354, AA5454, AA5554, AA5654, AA5654A,AA5754, AA5854, AA5954, AA5056, AA5356, AA5356A, AA5456, AA5456A,AA5456B, AA5556, AA5556A, AA5556B, AA5556C, AA5257, AA5457, AA5557,AA5657, AA5058, AA5059, AA5070, AA5180, AA5180A, AA5082, AA5182, AA5083,AA5183, AA5183A, AA5283, AA5283A, AA5283B, AA5383, AA5483, AA5086,AA5186, AA5087, AA5187, or AA5088.

Non-limiting exemplary 6xxx series aluminum alloys for use as the metalsubstrate can include AA6101, AA6101A, AA6101B, AA6201, AA6201A, AA6401,AA6501, AA6002, AA6003, AA6103, AA6005, AA6005A, AA6005B, AA6005C,AA6105, AA6205, AA6305, AA6006, AA6106, AA6206, AA6306, AA6008, AA6009,AA6010, AA6110, AA6110A, AA6011, AA6111, AA6012, AA6012A, AA6013,AA6113, AA6014, AA6015, AA6016, AA6016A, AA6116, AA6018, AA6019, AA6020,AA6021, AA6022, AA6023, AA6024, AA6025, AA6026, AA6027, AA6028, AA6031,AA6032, AA6033, AA6040, AA6041, AA6042, AA6043, AA6151, AA6351, AA6351A,AA6451, AA6951, AA6053, AA6055, AA6056, AA6156, AA6060, AA6160, AA6260,AA6360, AA6460, AA6460B, AA6560, AA6660, AA6061, AA6061A, AA6261,AA6361, AA6162, AA6262, AA6262A, AA6063, AA6063A, AA6463, AA6463A,AA6763, A6963, AA6064, AA6064A, AA6065, AA6066, AA6068, AA6069, AA6070,AA6081, AA6181, AA6181A, AA6082, AA6082A, AA6182, AA6091, or AA6092.

Non-limiting exemplary 7xxx series aluminum alloys for use as the metalsubstrate can include AA7011, AA7019, AA7020, AA7021, AA7039, AA7072,AA7075, AA7085, AA7108, AA7108A, AA7015, AA7017, AA7018, AA7019A,AA7024, AA7025, AA7028, AA7030, AA7031, AA7033, AA7035, AA7035A, AA7046,AA7046A, AA7003, AA7004, AA7005, AA7009, AA7010, AA7011, AA7012, AA7014,AA7016, AA7116, AA7122, AA7023, AA7026, AA7029, AA7129, AA7229, AA7032,AA7033, AA7034, AA7036, AA7136, AA7037, AA7040, AA7140, AA7041, AA7049,AA7049A, AA7149, AA7204, AA7249, AA7349, AA7449, AA7050, AA7050A,AA7150, AA7250, AA7055, AA7155, AA7255, AA7056, AA7060, AA7064, AA7065,AA7068, AA7168, AA7175, AA7475, AA7076, AA7178, AA7278, AA7278A, AA7081,AA7181, AA7185, AA7090, AA7093, AA7095, or AA7099.

Non-limiting exemplary 8xxx series aluminum alloys for use as the metalsubstrate cane include AA8005, AA8006, AA8007, AA8008, AA8010, AA8011,AA8011A, AA8111, AA8211, AA8112, AA8014, AA8015, AA8016, AA8017, AA8018,AA8019, AA8021, AA8021A, AA8021B, AA8022, AA8023, AA8024, AA8025,AA8026, AA8030, AA8130, AA8040, AA8050, AA8150, AA8076, AA8076A, AA8176,AA8077, AA8177, AA8079, AA8090, AA8091, or AA8093.

While aluminum alloy products are described throughout the disclosure,the methods and products apply to any metal substrate. In someembodiments, the metal substrate is aluminum, an aluminum alloy,magnesium, a magnesium-based material, titanium, a titanium-basedmaterial, copper, a copper-based material, steel, a steel-basedmaterial, bronze, a bronze-based material, brass, a brass-basedmaterial, a composite, a sheet used in composites, or any other suitablemetal or combination of materials. The product may include monolithicmaterials, as well as non-monolithic materials such as roll-bondedmaterials, clad materials, composite materials, or various othermaterials. In some examples, the metal substrate is a metal coil, ametal strip, a metal plate, a metal shate, a metal sheet, a metalbillet, a metal ingot, or other metal article.

The alloys can be produced by direct chill casting (including directchill co-casting) or semi-continuous casting, continuous casting(including, for example, by use of a twin belt caster, a twin rollcaster, a block caster, or any other continuous caster), electromagneticcasting, hot top casting, or any other casting method.

The metal substrate can be prepared from an alloy of any temper. In someembodiments, the metal substrate is an alloy in an F temper, a T4temper, or a T6 temper. As discussed below, the temper of the metalsubstrate may be altered by the thermal modification described herein.In one embodiment of the method, for example, a metal substrate isprovided in an F temper, a pretreatment film is produced on a surface ofthe metal substrate, and the pretreated metal substrate is heated suchthat the final corrosion resistant substrate is in a T6 temper withoutcompromising the pretreatment film.

Pretreatment

The methods described herein include producing a pretreatment film on asurface of the metal substrate to provide a pretreated metal substrate.The pretreatment films described herein improve properties, such asadhesion and/or corrosion resistance, of the metal substrates on thesurfaces of which the pretreatment films are produced.

The method of producing the pretreatment film on a surface of the metalsubstrate is not particularly limited, and any suitable method known inthe art may be used. In some embodiments, producing the pretreatmentfilm may comprise applying a pretreatment composition (e.g., aninorganic pretreatment composition) to the surface of the metalsubstrate. In some cases, for example, the pretreatment composition(e.g., an inorganic pretreatment composition) may be sprayed on asurface of the metal substrate. In some cases, the metal substrate maybe submerged in a pretreatment composition (e.g., an inorganicpretreatment composition). The pretreatment composition (e.g., aninorganic pretreatment composition) may be specially formulated toproduce a pretreatment film on the surface of the metal substrate. Forexample, the pretreatment composition may include chromium, molybdenum,titanium, zirconium, manganese, or combinations thereof.

In some embodiments, producing the pretreatment film may compriseanodizing a surface of the metal substrate. Anodizing may comprise, forexample, contacting the surface of the metal substrate with anelectrolyte solution and applying an electric current (e.g., alternatingcurrent (AC) power and/or direct current (DC)) to the metal substrate.In some cases, anodizing the metal substrates produces a pretreatedmetal substrate having a thin pretreatment film, which may comprise anoxide layer. Suitable methods for anodizing are described in U.S. Pub.No. 2020/0082972, which is incorporated herein by reference.

In some embodiments, producing the pretreatment film may comprise apyrogenic process. For example, the pretreatment film may be produced byflame pyrolysis deposition. Flame pyrolysis deposition may compriseburning (e.g., combusting) a metallic product to produce a deposit onthe surface of the metal substrate. The composition of the deposit willvary with the gas mixture and/or metallic compound, which may bespecially formulated for the flame pyrolysis deposition. In some cases,the deposit, which may comprise an oxide, forms a pretreatment film.

The composition or structure of the pretreatment film on the pretreatedmetal substrate is not particularly limited, and any pretreatment filmknown in the art may be produced or used. Pretreatment films known inthe art may be classified as organic pretreatment films, inorganicpretreatment films, and combination pretreatment films. Organicpretreatment films comprise an organic compound (i.e., acarbon-containing compound), such as organic polymers. Inorganicpretreatment films comprise an inorganic compound (i.e., a non-carboncontaining compound), such as metal ion analogues and metalliccoordination complexes. Combination pretreatment films comprise both anorganic compound and an inorganic compound or an organic-inorganiccompound that includes both organic and inorganic moieties.

In some embodiments, the pretreatment film produced in the disclosedmethods is an organic pretreatment film. Preferably, however, thepretreatment film is an inorganic pretreatment film or a combinationpretreatment film. As described herein, thermal modification (discussedbelow) of metal substrates that have been pretreated with inorganicand/or combination pretreatment films surprisingly improves properties(e.g., adhesion, corrosion resistance) of the metal substrates. On thecontrary, the present inventors have found that thermal modification ofmetal substrates that have been pretreated with organic pretreatmentfilms may not improve properties (e.g., may not improve properties tothe same degree). In some cases, the thermal modification of metalsubstrates having an organic pretreatment film may even degradeproperties of the substrate. It is theorized that organic compoundspresent in conventional organic pretreatment films (e.g., organicpolymers) may undergo undesirable chemical reactions (e.g., combustion)when subjected to the thermal modification described herein. Thus, insome embodiments of the methods, the pretreatment film is not an organicpretreatment film (i.e., a pretreatment film including an organiccompound only).

In some cases, producing the pretreatment film on a surface of the metalsubstrate comprises creating an oxide layer on the surface. Said anotherway, the pretreatment film may comprise an oxide layer. For example, thepretreatment film may comprise an inorganic oxide layer. The oxide layercomprises one or more oxides, such as metallic oxides.

The composition of the oxide layer is not particularly limited, and anysuitable oxide layer known in the art may be used. The oxide layer maycomprise, for example, an aluminum oxide (e.g., Al₂O, AlO, and/orAl₂O₃), a silicon oxide (e.g., SiO₂ and/or SiO), a titanium oxide (e.g.,Ti₂O, TiO, Ti₂O₃, and/or TiO₂), a chromium oxide (e.g., CrO, Cr₂O₃,CrO₂, and/or CrO₅), a manganese oxide (e.g., MnO, Mn₃O₄, Mn₂O₃, MnO₂,MnO₃, and/or Mn₂O₇), a nickel oxide (e.g., NiO and/or Ni₂O₃), a yttriumoxide (e.g., Y₂O₃), a zirconium oxide (e.g., ZrO₂), a molybdenum oxide(e.g., MoO₂ and/or MoO₃), or combinations thereof.

In some embodiments, the pretreatment film comprises an oxide layer ofaluminum oxide. In some embodiments, the pretreatment film comprises anoxide layer of silicon oxide. In some embodiments, the pretreatment filmcomprises a combination of oxides. For example, the pretreatment filmmay comprise on oxide layer of titanium oxide and zirconium oxide.

Generally, the pretreatment film comprises a thin layer on a portion(e.g., at least a portion) of a surface of the metal substrate. In somecases, the pretreatment film may be produced on one surface of the metalsubstrate. In some cases, the pretreatment film may be produced on oneor more surfaces of the metal substrate, e.g., two surfaces. In somecases, the pretreatment film is produced on all surfaces of the metalsubstrate.

The thickness of the pretreatment film may vary. As noted, thepretreatment film is generally a thin layer. The thickness of thepretreatment film can range from about 1 nm to about 1000 nm. In somecases, the pretreatment film is less than about 1000 nm in thickness,e.g., less than about 900 nm, less than about 800 nm, less than about700 nm, less than about 600 nm, less than about 500 nm, less than about400 nm, less than about 300 nm, less than about 200 nm, or less thanabout 100 nm. For example, the pretreatment film can be from about 5 nmto about 1000 nm, from about 10 nm to about 900 nm, from about 20 nm toabout 800 nm, or from about 30 nm to about 700 nm in thickness. In someexamples, the pretreatment film can be about 1 nm, about 5 nm, about 10nm, about 15 nm, about 20 nm, about 25 nm, about 30 nm, about 35 nm,about 40 nm, about 45 nm, about 50 nm, about 55 nm, about 60 nm, about65 nm, about 70 nm, about 75 nm, about 80 nm, about 85 nm, about 90 nm,about 95 nm, about 100 nm, about 150 nm, about 200 nm, about 250 nm,about 300 nm, about 400 nm, about 500 nm, about 600, about 700 nm, about750 nm, about 800 nm, about 850 nm, about 900 nm, about 950 nm, or about1000 nm in thickness, or anywhere in between.

In some cases, the pretreatment film on the pretreated metal substratemay be composed of multiple layers. In particular, certain methods ofproducing the pretreatment film may produce distinct layers within thepretreatment film. For example, anodizing the metal substrate mayproduce a pretreatment film including a barrier layer (e.g., composed ofaluminum oxide, such as nonporous aluminum oxide) and a filament layer(e.g., composed of aluminum oxide, such porous aluminum oxide). Thecharacteristics of either layer may be controlled by the method ofproducing the pretreatment film (e.g., the anodizing parameters orconditions).

The temper of the substrate is generally not affected (e.g., altered) byproducing the pretreatment film. That is, the pretreated metal substrategenerally is in the same temper as the metal substrate beforepretreatment. In some embodiments, the pretreated metal substrate is analloy in an F temper, a T4 temper, or a T6 temper. As discussed below,the temper of the metal substrate may be altered by the thermalmodification described herein. In one embodiment, for example, thepretreated metal substrate is in F temper, and the thermal modificationof the pretreated metal substrate produces a substrate in a T6 temper.

Thermal Modification

The methods described herein include heating the pretreated metalsubstrate to provide the corrosion resistant substrate. As noted above,conventional methods of pretreating metal substrates avoid exposing themetal substrate to high temperatures (e.g., temperatures greater than400° C.) after a pretreatment film has been produced. It was believed bythose of ordinary skill in the art that exposure to high temperatureswould degrade the pretreatment film or otherwise reduce theeffectiveness of the pretreatment film. On the contrary, heating apretreated metal substrate according to the methods described hereinenhances the pretreatment film.

The thermal modification of the present disclosure includes heating thepretreated metal substrate at a first temperature, which is generally ahigh temperature relative to conventional methods. In some embodiments,the first temperature is from 300° C. to 550° C., e.g., from 300° C. to540° C., from 300° C. to 530° C., from 300° C. to 520° C., from 300° C.to 510° C., from 300° C. to 500° C., from 325° C. to 550° C., from 325°C. to 540° C., from 325° C. to 530° C., from 325° C. to 520° C., from325° C. to 510° C., from 325° C. to 500° C., from 350° C. to 550° C.,from 350° C. to 540° C., from 350° C. to 530° C., from 350° C. to 520°C., from 350° C. to 510° C., from 350° C. to 500° C., from 375° C. to550° C., from 375° C. to 540° C., from 375° C. to 530° C., from 375° C.to 520° C., from 375° C. to 510° C., from 375° C. to 500° C., from 400°C. to 550° C., from 400° C. to 540° C., from 400° C. to 530° C., from400° C. to 520° C., from 400° C. to 510° C., from 400° C. to 500° C.,from 425° C. to 550° C., from 425° C. to 540° C., from 425° C. to 530°C., from 425° C. to 520° C., from 425° C. to 510° C., from 425° C. to500° C., from 450° C. to 550° C., from 450° C. to 540° C., from 450° C.to 530° C., from 450° C. to 520° C., from 450° C. to 510° C., or from450° C. to 500° C.

In terms of upper limits, the first temperature may be less than 550°C., e.g., less than 540° C., less than 530° C., less than 520° C., lessthan 510° C., or less than 500° C. In terms of lower limits, the firsttemperature may be greater than 300° C., e.g., greater than 325° C.,greater than 350° C., greater than 375° C., greater than 400° C.,greater than 425° C., or greater than 450° C.

In some cases, the first temperature may be about 375° C., about 385°C., about 395° C., about 400° C., about 405° C., about 410° C., about415° C., about 420° C., about 425° C., about 430° C., about 435° C.,about 440° C., about 445° C., about 450° C., about 455° C., about 460°C., about 465° C., about 466° C., about 467° C., about 468° C., about469° C., about 470° C., about 471° C., about 472° C., about 473° C.,about 474° C., about 475° C., about 476° C., about 477° C., about 478°C., about 479° C., about 480° C., about 481° C., about 482° C., about483° C., about 484° C., about 485° C., about 486° C., about 487° C.,about 488° C., about 489° C., about 490° C., about 491° C., about 492°C., about 493° C., about 494° C., about 495° C., about 496° C., about497° C., about 498° C., about 499° C., about 500° C., about 510° C.,about 520° C., about 525° C., about 530° C., about 540° C., or about550° C., or any temperature therebetween.

The thermal modification of the described methods may include prolongedexposure to high temperatures, e.g., the first temperature. Prolongedexposure to high temperatures may enhance the pretreatment film, e.g.,by (further) drying and/or densifying the pretreatment film. Thus, insome embodiments, the pretreated metal substrate may be heated at thefirst temperature for a period of time.

In some embodiments, the pretreated metal substrate is heated at thefirst temperature for a period of time from 10 seconds to 30 minutes,e.g., from 10 seconds to 25 minutes, from 10 seconds to 20 minutes, from10 seconds to 15 minutes, from 10 seconds to 10 minutes, from 15 secondsto 30 minutes, from 15 seconds to 25 minutes, from 15 seconds to 20minutes, from 15 seconds to 15 minutes, from 15 seconds to 10 minutes,from 30 seconds to 30 minutes, from 30 seconds to 25 minutes, from 30seconds to 20 minutes, from 30 seconds to 15 minutes, from 30 seconds to10 minutes, from 60 seconds to 30 minutes, from 60 seconds to 25minutes, from 60 seconds to 20 minutes, from 60 seconds to 15 minutes,from 60 seconds to 10 minutes, from 75 seconds to 30 minutes, from 75seconds to 25 minutes, from 75 seconds to 20 minutes, from 75 seconds to15 minutes, from 75 seconds to 10 minutes, from 90 seconds to 30minutes, from 90 seconds to 25 minutes, from 90 seconds to 20 minutes,from 90 seconds to 15 minutes, or from 90 seconds to 10 minutes.

In terms of upper limits, the pretreated metal substrate may be heatedat the first temperature for less than 30 minutes, e.g., less than 25minutes, less than 20 minutes, less than 15 minutes, or less than 10minutes. In terms of lower limits, the pretreated metal substrate may beheated at the first temperature for at least 10 seconds, e.g., at least15 seconds, at least 30 seconds, at least 60 seconds, at least 75seconds, or at least 90 seconds.

In some cases, for example, the pretreated metal substrate is heated atthe first temperature for about 1 minute, about 2 minutes, about 3minutes, about 4 minutes, about 5 minutes, about 6 minutes, about 7minutes, about 8 minutes, about 9 minutes, or about 10 minutes, or anylength of time therebetween.

In some embodiments, the first temperature may be maintained during theperiod of time by an appropriate heating process. In some cases, forexample, heat may be continuously and/or continually applied to thepretreated metal substrate for the period of time.

In some embodiments, the first temperature may not be maintained duringthe period of time. In some cases, for example, the pretreated metalsubstrate may be exposed to the first temperature, and no additionalheat may be applied during the period of time, such that the temperatureat which the pretreated metal substrate is heated during the period oftime may diminish slightly, e.g., by less than 25° C., less than 20° C.,less than 15° C., less than 10° C., less than 5° C., less than 3° C.,less than 2° C., or less than 1° C.

In some embodiments, the thermal modification includes additionalheating steps. For example, the pretreated metal substrate may be heatedat a second temperature (e.g., before and/or after having been heated atthe first temperature). In some cases, heating at the secondtemperature, according to the described methods, further enhances thepretreatment film, e.g., by drying and/or densifying the pretreatmentfilm. As a result, the corrosion resistant substrate may demonstrateimproved adhesion, bond durability, and/or corrosion resistance.

The second temperature is generally a higher temperature relative toconventional methods. The second temperature may or may not be relatedto the first temperature. In some embodiments, for example, the secondtemperature is less than the first temperature. In some embodiments, thefirst temperature and the second temperature are about the same.

In some embodiments, the second temperature is from 75° C. to 250° C.,e.g., from 75° C. to 240° C., from 75° C. to 230° C., from 75° C. to220° C., from 75° C. to 210° C., from 75° C. to 200° C., from 80° C. to250° C., from 80° C. to 240° C., from 80° C. to 230° C., from 80° C. to220° C., from 80° C. to 210° C., from 80° C. to 200° C., from 85° C. to250° C., from 85° C. to 240° C., from 85° C. to 230° C., from 85° C. to220° C., from 85° C. to 210° C., from 85° C. to 200° C., from 90° C. to250° C., from 90° C. to 240° C., from 90° C. to 230° C., from 90° C. to220° C., from 90° C. to 210° C., from 90° C. to 200° C., from 95° C. to250° C., from 95° C. to 240° C., from 95° C. to 230° C., from 95° C. to220° C., from 95° C. to 210° C., from 95° C. to 200° C., from 100° C. to250° C., from 100° C. to 240° C., from 100° C. to 230° C., from 100° C.to 220° C., from 100° C. to 210° C., or from 100° C. to 200° C. In someembodiments, the second temperature is from 150° C. to 250° C., e.g.,from 150° C. to 240° C., from 150° C. to 230° C., from 150° C. to 220°C., from 150° C. to 210° C., from 150° C. to 200° C., from 155° C. to250° C., from 155° C. to 240° C., from 155° C. to 230° C., from 155° C.to 220° C., from 155° C. to 210° C., from 155° C. to 200° C., from 160°C. to 250° C., from 160° C. to 240° C., from 160° C. to 230° C., from160° C. to 220° C., from 160° C. to 210° C., from 160° C. to 200° C.,from 165° C. to 250° C., from 165° C. to 240° C., from 165° C. to 230°C., from 165° C. to 220° C., from 165° C. to 210° C., from 165° C. to200° C., from 170° C. to 250° C., from 170° C. to 240° C., from 170° C.to 230° C., from 170° C. to 220° C., from 170° C. to 210° C., from 170°C. to 200° C., from 175° C. to 250° C., from 175° C. to 240° C., from175° C. to 230° C., from 175° C. to 220° C., from 175° C. to 210° C.,from 175° C. to 200° C., from 180° C. to 250° C., from 180° C. to 240°C., from 180° C. to 230° C., from 180° C. to 220° C., from 180° C. to210° C., or from 180° C. to 200° C.

In terms of upper limits, the second temperature may be less than 250°C., e.g., less than 240° C., less than 230° C., less than 220° C., lessthan 210° C., or less than 200° C. In terms of lower limits, the secondtemperature may be greater than 75° C., e.g., greater than 80° C.,greater than 85° C., greater than 90° C., greater than 95° C., orgreater than 100° C.

In some cases, for example, the second temperature may be about 90° C.,about 91° C., about 92° C., about 93° C., about 94° C., about 95° C.,about 96° C., about 97° C., about 98° C., about 99° C., about 100° C.,about 101° C., about 102° C., about 103° C., about 104° C., about 105°C., about 106° C., about 107° C., about 108° C., about 109° C., about110° C., about 111° C., about 112° C., about 113° C., about 114° C.,about 115° C., about 116° C., about 117° C., about 118° C., about 119°C., about 120° C., about 121° C., about 122° C., about 123° C., about124° C., about 125° C., about 126° C., about 127° C., about 128° C.,about 129° C., about 130° C., about 131° C., about 132° C., about 133°C., about 134° C., about 135° C., about 136° C., about 137° C., about138° C., about 139° C., about 140° C., about 141° C., about 142° C.,about 143° C., about 144° C., about 145° C., about 146° C., about 147°C., about 148° C., about 149° C., or about 150° C., or any temperaturetherebetween.

As with the first temperature, in some cases, the pretreated metalsubstrate may be heated at the second temperature for a prolonged time.In some embodiments, the pretreated metal substrate is heated at thesecond temperature for a period of time greater than the time it isexposed to the first temperature. In some embodiments, the preheatedmetal substrate is heated at the second temperature for a period of timeless than the time it is exposed to the first temperature. In someembodiments, the pretreated metal substrate is exposed to the firsttemperature and the second temperature for about the same amounts oftime.

In some embodiments, the pretreated metal substrate is heated at thesecond temperature for a period of time from 1 hour to 48 hours, e.g.,from 1 hour to 42 hours, from 1 hour to 38 hours, from 1 hour to 34hours, from 1 hour to 30 hours, from 2 hours to 48 hours, from 2 hoursto 42 hours, from 2 hours to 38 hours, from 2 hours to 34 hours, from 2hours to 30 hours, from 4 hours to 48 hours, from 4 hours to 42 hours,from 4 hours to 38 hours, from 4 hours to 34 hours, from 4 hours to 30hours, from 8 hours to 48 hours, from 8 hours to 42 hours, from 8 hoursto 38 hours, from 8 hours to 34 hours, from 8 hours to 30 hours, from 12hours to 48 hours, from 12 hours to 42 hours, from 12 hours to 38 hours,from 12 hours to 34 hours, from 12 hours to 30 hours, from 18 hours to48 hours, from 18 hours to 42 hours, from 18 hours to 38 hours, from 18hours to 34 hours, from 18 hours to 30 hours, from 22 hours to 48 hours,from 22 hours to 42 hours, from 22 hours to 38 hours, from 22 hours to34 hours, or from 22 hours to 30 hours.

In terms of upper limits, the pretreated metal substrate may be heatedat the second temperature for less than 48 hours, e.g., less than 42hours, less than 38 hours, less than 34 hours, or less than 30 hours. Interms of lower limits, the pretreated metal substrate may be heated atthe second temperature for at least 1 hour, e.g., at least 2 hours, atleast 4 hours, at least 8 hours, at least 12 hours, at least 18 hours,or at least 22 hours.

In some cases, for example, the pretreated metal substrate is heated atthe second temperature for about 18 hours, about 19 hours, about 20hours, about 21 hours, about 22 hours, about 23 hours, about 24 hours,about 25 hours, about 26 hours, about 27 hours, about 28 hours, about 29hours, about 30 hours, about 31 hours, or about 32 hours, or any lengthof time therebetween.

As with the first temperature, in some embodiments, the secondtemperature may be maintained during the period of time by anappropriate heating process. In some cases, for example, heat may becontinuously and/or continually applied to the pretreated metalsubstrate for a period of time. In some embodiments, the secondtemperature may not be maintained during the period of time. In somecases, for example, the pretreated metal substrate may be exposed to thesecond temperature, and no additional heat may be applied during theperiod of time, such that the temperature at which the pretreated metalsubstrate is heated during the period of time may diminish slightly,e.g., by less than 25° C., less than 20° C., less than 15° C., less than10° C., less than 5° C., less than 3° C., less than 2° C., or less than1° C.

The thermal modification of the described methods may artificially agethe pretreated metal substrate. That is, the corrosion resistantsubstrate produced by the methods described herein may be anartificially aged alloy. Artificial aging may be accomplished, forexample, by heating the pretreated metal substrate at the firsttemperature alone and/or by heating the pretreated metal substrate atboth the first temperature and the second temperature.

By artificially aging the pretreated metal substrate, the thermalmodification described herein produces a corrosion resistant substratein a different temper from that of the metal substrate and/or thepretreated metal substrate. In some embodiments, for example, the metalsubstrate is in an F temper or a T4 temper, and the thermal modificationproduces a substrate in a T6 temper. Further discussion of the temper ofthe corrosion resistant substrate is provided below.

Corrosion Resistant Substrate

The methods described herein produce a corrosion resistant substrate. Inparticular, the methods produce a corrosion resistant substrate having apretreatment film (e.g., an enhanced pretreatment film, such as a driedpretreatment film or a densified pretreatment film). The pretreatmentfilm imparts desirable characteristics, such as corrosion resistanceand/or increased adhesion, on the corrosion resistant substrate. As aresult of the described methods, the corrosion resistant substratedemonstrates excellent bond durability, adhesion, and/or corrosionresistance.

In some embodiments, the thermal modification does not alter (e.g.,chemically alter) the pretreatment film. In some cases, for example, thechemical composition of the pretreatment film is substantially unchangedby the thermal modification. In some cases, the thermal modificationdries the pretreatment film (e.g., removes adsorbed and/or absorbedwater). The pretreatment film of the corrosion resistant substrate maycomprise an oxide layer. For example, the pretreatment film of thecorrosion resistant substrate may comprise an inorganic oxide layer. Theoxide layer comprises one or more oxides, such as metallic oxides. Inparticular, the pretreatment film of the corrosion resistant substratemay comprise any of the oxides discussed above or combinations thereof.

In some cases, exposing an aluminum alloy to high temperatures causessurface enrichment of certain alloying elements. For example, hightemperatures typically cause surface enrichment of magnesium and/orsilicon, which can contribute to corrosion. Surface enrichment of theseand other elements is not an issue for the thermal modification of thepresent disclosure, because the pretreatment film (e.g., the oxidelayer) may act as a barrier.

In some cases, the physical structure of the pretreatment film afterthermal modification is unchanged as compared to the physical structureof the pretreatment film before the thermal modification as describedherein. In some cases, the thermal modification forms metal-oxidebridges, producing a dense, anhydrous oxide film. As noted above, thepretreatment film on the pretreated metal substrate may be composed ofmultiple layers. These layers may remain intact after the thermalmodification. For example, the corrosion resistant substrate may includea pretreatment film including a barrier layer (e.g., composed ofaluminum oxide, such as nonporous aluminum oxide) and a filament layer(e.g., composed of aluminum oxide, such porous aluminum oxide).

As noted above, thermal modification may artificially age the pretreatedmetal substrate. Thus, the corrosion resistant substrate may be in atemper corresponding to an artificially aged alloy. In some embodiments,the corrosion resistant substrate is in a T5 temper, a T6 temper, a T61temper, a T7 temper, T8x temper, or a T9 temper. In some cases, inparticular, the corrosion resistant substrate may be in a T6 temper.

Use of Corrosion Resistant Substrate

The corrosion resistant substrates made according to the methodsdescribed herein can be used in producing products, including productsfor use in, among others, automotive, electronics, and transportationapplications, such as commercial vehicle, aircraft, or railwayapplications. The continuous coils and methods described herein provideproducts with surface properties desired in various applications. Theproducts described herein can have high strength, high deformability(elongation, stamping, shaping, formability, bendability, or hotformability), and/or high resistance to corrosion. Preparing thecorrosion resistant substrate as a continuous coil provides a productthat is deformable without damaging the pretreatment.

In certain aspects, the corrosion resistant substrates can be coated,e.g., Zn-phosphated and electrocoated (E-coated). The corrosionresistant substrates display an improved adhesion of coatings ascompared to continuous coils that do not contain a pretreatment film.

In some further aspects, the corrosion resistant substrates display ahigh level of adhesion of laminates or lacquer films onto the surface ofthe continuous coils. Additionally, laminates and lacquers can be curedafter application at temperatures of up to about 230° C. The corrosionresistant substrates are not damaged by elevated temperatures used incertain downstream processing of aluminum alloy products, providing athermally resistant pretreatment for aluminum alloy products.

In some further aspects, the corrosion resistant substrates displayexcellent bond durability.

In some examples, the corrosion resistant substrates can be used forchassis, cross-member, and intra-chassis components (encompassing, butnot limited to, all components between the two C channels in acommercial vehicle chassis) to gain strength, serving as a full orpartial replacement of high-strength steels. In certain aspects, thecorrosion resistant substrates can be used to prepare motor vehicle bodypart products, e.g., automobile body parts, such as bumpers, side beams,roof beams, cross beams, pillar reinforcements (e.g., A-pillars,B-pillars, and C-pillars), inner panels, side panels, floor panels,tunnels, structure panels, reinforcement panels, inner hoods, or trunklid panels. The disclosed corrosion resistant substrates can also beused in aircraft or railway vehicle applications, to prepare, forexample, external and internal panels.

In some examples, the corrosion resistant substrates can also be used toprepare housings for electronic devices, including mobile phones andtablet computers. For example, the corrosion resistant substrates can beused to prepare housings for the outer casing of mobile phones (e.g.,smart phones) and tablet bottom chassis. Exemplary consumer electronicproducts include mobile phones, audio devices, video devices, cameras,laptop computers, desktop computers, tablet computers, televisions,displays, household appliances, video playback and recording devices,and the like. Exemplary consumer electronic product parts include outerhousings (e.g., facades) and inner pieces for the consumer electronicproducts.

The corrosion resistant substrates can be used in any other desiredapplication.

Illustrations

Illustration 1 is a method of making a corrosion resistant substrate,the method comprising: producing a pretreatment film on a surface of ametal substrate to provide a pretreated metal substrate; and heating thepretreated metal substrate at a first temperature to provide thecorrosion resistant substrate, wherein the first temperature is greaterthan 300° C.; and wherein the metal substrate and/or the pretreatedmetal substrate is in an F temper, a T4 temper, or a T6 temper.

Illustration 2 is the method of any preceding or subsequentillustration, wherein the metal substrate comprises an aluminum alloy.

Illustration 3 is the method of any preceding or subsequentillustration, wherein the metal substrate comprises a 5xxx seriesaluminum alloy, a 6xxx series aluminum alloy, or a 7xxx series aluminumalloy.

Illustration 4 is the method of any preceding or subsequentillustration, wherein the corrosion resistant substrate is in a T6temper.

Illustration 5 is the method of any preceding or subsequentillustration, wherein the pretreatment film comprises an oxide layer.

Illustration 6 is the method of any preceding or subsequentillustration, wherein the oxide layer comprises an aluminum oxide, asilicon oxide, a titanium oxide, a chromium oxide, a manganese oxide, anickel oxide, a yttrium oxide, a zirconium oxide, a molybdenum oxide, orcombinations thereof.

Illustration 7 is the method of any preceding or subsequentillustration, wherein producing the pretreatment film comprises applyingan inorganic pretreatment composition to the surface of the metalsubstrate.

Illustration 8 is the method of any preceding or subsequentillustration, wherein producing the pretreatment film comprisesanodizing the surface of the metal substrate.

Illustration 9 is the method of any preceding or subsequentillustration, wherein producing the pretreatment film comprises flamehydrolyzing the surface of the metal substrate.

Illustration 10 is the method of any preceding or subsequentillustration, wherein the first temperature is from 300° C. to 550° C.

Illustration 11 is the method of any preceding or subsequentillustration, wherein the heating comprises heating the pretreated metalsubstrate at the first temperature for less than 30 minutes.

Illustration 12 is the method of any preceding or subsequentillustration, wherein the heating further comprises heating thepretreated metal substrate at a second temperature.

Illustration 13 is the method of any preceding or subsequentillustration, wherein the second temperature is lower than the firsttemperature.

Illustration 14 is the method of any preceding or subsequentillustration, wherein the second temperature is from 75° C. to 250° C.

Illustration 15 is the method of any preceding or subsequentillustration, wherein the heating comprises heating the pretreated metalsubstrate at the second temperature from 1 hour to 48 hours.

Illustration 16 is the method of any preceding or subsequentillustration, wherein the metal substrate is a continuous coil.

Illustration 17 is a corrosion resistant coil comprising: an aluminumalloy continuous coil, wherein a surface of the aluminum alloycontinuous coil comprises an inorganic pretreatment film, and whereinthe aluminum alloy continuous coil is in an F temper, a T4 temper, or aT6 temper.

Illustration 18 is the method of any preceding or subsequentillustration, wherein the aluminum alloy continuous coil comprises a5xxx series aluminum alloy, a 6xxx series aluminum alloy, or a 7xxxseries aluminum alloy.

Illustration 19 is the corrosion resistant coil of any preceding orsubsequent illustration, wherein the inorganic pretreatment filmcomprises an oxide layer.

Illustration 20 is the corrosion resistant coil of any preceding orsubsequent illustration, wherein the oxide layer comprises an aluminumoxide, a silicon oxide, a titanium oxide, a chromium oxide, a manganeseoxide, a nickel oxide, a yttrium oxide, a zirconium oxide, a molybdenumoxide, or combinations thereof.

Illustration 21 is a method of making a corrosion resistant substrate,the method comprising producing a pretreatment film on a surface of ametal substrate to provide a pretreated metal substrate; and heating thepretreated metal substrate at a first temperature to provide thecorrosion resistant substrate, wherein the metal substrate and/or thepretreated metal substrate is in an F temper, and wherein the corrosionresistant substrate is in a T5 temper, a T6 temper, a T61 temper, a T7temper, T8x temper, or a T9 temper.

EXAMPLES

The following examples will serve to further illustrate the presentinvention without, however, constituting any limitation thereof. On thecontrary, it is to be clearly understood that resort may be had tovarious embodiments, modifications, and equivalents thereof which, afterreading the description herein, may suggest themselves to those ofordinary skill in the art without departing from the spirit of theinvention.

Example 1: Bond Durability Testing

As noted above, the thermal modification method described hereinproduces corrosion resistant substrates that demonstrate excellent bonddurability. This example serves to illustrate the improvement of thebond durability of corrosion resistant substrates produced according tothe methods described herein relative to metallic substrates pretreatedaccording to conventional methods and not thermally modified.

Several samples of a corrosion resistant substrate were preparedaccording to the disclosed methods using an AA7075 aluminum alloy totest the properties of the corrosion resistant substrate. Each of thesamples tested is shown in Table 1. Samples were prepared with varyingpretreatment methods and comprising varying components, as indicated inTable 1. Furthermore, samples were prepared from varying tempers, asindicated in Table 1. Each sample was subjected to thermal modificationas follows: each sample was heated at 485° C. for 5 minutes, andsubsequently heated at 125° C. for 24 hours. Following this thermalmodification, each sample was in a T6 temper.

As shown in Table 1, several comparative samples (Comp. 1-7) were alsoprepared and tests. The comparative samples were prepared by producing apretreatment film. These samples did not undergo thermal modification.

TABLE 1 Intl. Pretreatment Final Sample ID Temper Film ThermalModification Temper Sample 1 F Anodized, 485° C. for 5 minutes; T6 AlOxide 125° C. for 24 hours Sample 2 F Anodized, 485° C. for 5 minutes;T6 Al Oxide 125° C. for 24 hours Sample 3 F Anodized, 485° C. for 5minutes; T6 Al Oxide 125° C. for 24 hours Sample 4 T6 Anodized, 485° C.for 5 minutes; T6 Al Oxide 125° C. for 24 hours Sample 5 T6 Anodized,485° C. for 5 minutes; T6 Al Oxide 125° C. for 24 hours Sample 6 T6Anodized, 485° C. for 5 minutes; T6 Al Oxide 125° C. for 24 hours Sample7 F Flame 485° C. for 5 minutes; T6 hydrolyzed, 125° C. for 24 hours SiOxide Sample 8 F Flame 485° C. for 5 minutes; T6 hydrolyzed, 125° C. for24 hours Si Oxide Sample 9 F Flame 485° C. for 5 minutes; T6 hydrolyzed,125° C. for 24 hours Si Oxide Sample 10 F Flame 485° C. for 5 mins; T6hydrolyzed, 125° C. for 24 hours Si Oxide Sample 11 F Inorg. 485° C. for5 mins; T6 composition, 125° C. for 24 hours Ti Oxide/Zr Oxide Sample 12F Combination 485° C. for 5 mins; T6 (org. & inorg.) 125° C. for 24hours pretreatment Sample 13 F Combination 485° C. for 5 mins; T6 (org.& inorg.) 125° C. for 24 hours pretreatment Comp. 1 T6 Anodized, N/A T6Al Oxide Comp. 2 T6 Anodized, N/A T6 Al Oxide Comp. 3 T6 Anodized, N/AT6 Al Oxide Comp. 4 T6 Anodized, N/A T6 Al Oxide Comp. 5 T6 Anodized,N/A T6 Al Oxide Comp. 6 T6 Anodized, N/A T6 Al Oxide Comp. 7 T6 FlameN/A T6 hydrolyzed, Si Oxide

The above samples and comparatives were subjected to bond durabilitytesting. In this testing, a set of six lap joints/bonds of each samplewere connected in sequence by bolts and positioned vertically in a 90%relative humidity (RH) humidity cabinet. The temperature was maintainedat 50° C. A force load of 2.4 kN was applied to the bond sequence. Thebond durability test is a cyclic exposure test that is conducted for upto 60 cycles. Each cycle lasts for 24 hours. In each cycle, the bondsare exposed in the humidity cabinet for 22 hours, then immersed in 5%NaCl for 15 minutes, and finally air-dried for 105 minutes. Upon thebreaking of four joints, the test is discontinued for the particular setof joints and is indicated as a bond failure. For this disclosure, thecompletion of 45 cycles without a bond failure indicates that the set ofjoints passed the bond durability test. Upon the completion of 60cycles, the test is discontinued.

The bond durability test results are shown below in Table 2. In Table 2,each of the joints are numbered 1 through 6, where joint 1 is the topjoint and joint 6 is the bottom joint when oriented vertically. Unlessotherwise noted, the number in the cells indicates the number ofsuccessful cycles before a break. An asterisk (“*”) next to a numberindicates that the joint was unbroken but that the test wasdiscontinued. The results are summarized in Table 2 below:

TABLE 2 Bond Durability Test Coupon Arrangement 1 6 Trial Sample Top 2 34 5 Bottom  1 Sample 1 60* 60* 60* 60*  60*  60*  2 Sample 2 60* 60* 60*60*  60*  60*  3 Sample 3 60* 60* 60* 60*  60*  60*  4 Sample 4 53* 46 53* 45  53 50  5 Sample 5 40* 40* 39  40  34 29  6 Sample 6 47* 24  47*27  47 26  7 Sample 7 60* 60  59  60* 59  60*  8 Sample 8 52* 52* 49 48  52 50  9 Sample 9 51* 44  50  49  51  51* 10 Sample 10 57* 52  57 50   57* 56 11 Sample 11 60* 60* 60* 60*  60*  60* 12 Sample 12  7*  7*6 7  7  5 13 Sample 13 10* 10* 10  8  8  9 14 Comp. 1  7*  7* 5 5  7  615 Comp. 2 21* 21* 16  13  15 21 16 Comp. 3 10* 10* 10  7  7  5 17 Comp.4 10* 8 9 10* 10  6 18 Comp. 5 11* 11* 11  9  5 10 19 Comp. 6 25* 25*24  25  23 15 20 Comp. 7 2  4*  4* 4  4  4

The exemplary corrosion resistant substrates which were subjected tothermal modification according to the present disclosure demonstratedexcellent bond durability, with all but three samples (Sample 5, Sample12, and Sample 13) passing the test. Notably, two of the three samplesthat did not pass the durability test included organic pretreatmentfilms. The comparative substrates demonstrated comparatively poorer bonddurability, with each comparative substrate failing the durability test.

Example 2: Bond Durability Testing

This example further illustrates the improvement of the bond durabilityof corrosion resistant substrates produced according to the methodsdescribed herein relative to metallic substrates pretreated according toconventional methods and not thermally modified.

Several samples of a corrosion resistant substrate were preparedaccording to the disclosed methods using an AA7075 aluminum alloy totest the properties of the corrosion resistant substrate. Each of thesamples tested is shown in Table 3. Samples were prepared by etchingwith an acid and applying a varying titanium/zirconium pretreatment(Gardobond 4591 from Chemetall GmbH (Frankfurt, Germany)), as detailedin Table 3. Each sample was prepared at an initial F temper. Each samplewas thermally modified to adjust the temper, as indicated in Table 3.

TABLE 3 Intl. Pretreatment Thermal Final Sample ID Temper Acid Etch FilmModification Temper Sample 14 F 0.2 g/m², Ti: 22 mg/m², 125° C. for T665° C., Zr: 20 mg/m², 24 hours 5 seconds 5 seconds 25° C. Sample 15 F0.2 g/m², Ti: 22 mg/m², 125° C. for T6 65° C., Zr: 20 mg/m², 24 hours 5seconds 5 seconds 25° C. Sample 16 F 0.2 g/m², Ti: 17 mg/m², 125° C. forT6 50° C., Zr: 11 mg/m², 24 hours 1 second 10 seconds 25° C. Sample 17 F0.2 g/m², Ti: 17 mg/m², 125° C. for T6 50° C., Zr: 11 mg/m², 24 hours 1second 10 seconds 25° C. Sample 18 F 0.8 g/m², Ti: 13 mg/m², 125° C. forT6 50° C., Zr: 8 mg/m², 24 hours 5 seconds 10 second 25° C. Sample 19 F0.8 g/m², Ti: 13 mg/m², 125° C. for T6 50° C., Zr: 8 mg/m², 24 hours 5seconds 10 seconds 25° C. Sample 20 F 0.2 g/m², Ti: 42 mg/m², 125° C.for T6 50° C., Zr: 20 mg/m², 24 hours 1 second 10 seconds 45° C. Sample21 F 0.2g/m², Ti: 42 mg/m², 125° C. for T6 50° C., Zr: 20 mg/m², 24hours 1 second 10 seconds 45° C. Sample 22 F 0.2 g/m², Ti: 16 mg/m²,125° C. for T6 50° C., Zr: 12 mg/m², 24 hours 1 second 10 seconds 25° C.Sample 23 F 0.2 g/m², Ti: 16 mg/m², 125° C. for T6 50° C., Zr: 12 mg/m²,24 hours 1 second 10 seconds 25° C.

The above samples were subjected to bond durability testing. In thistesting, a set of six lap joints/bonds of each sample were connected insequence by bolts and positioned vertically in a 90% relative humidity(RH) humidity cabinet. The temperature was maintained at 50° C. A forceload of 2.4 kN was applied to the bond sequence. The bond durabilitytest is a cyclic exposure test that is conducted for up to 60 cycles.Each cycle lasts for 24 hours. In each cycle, the bonds are exposed inthe humidity cabinet for 22 hours, then immersed in 5% NaCl for 15minutes, and finally air-dried for 105 minutes. Upon the breaking offour joints, the test is discontinued for the particular set of jointsand is indicated as a bond failure. For this disclosure, the completionof 45 cycles without a bond failure indicates that the set of jointspassed the bond durability test. Upon the completion of 60 cycles, thetest is discontinued.

The bond durability test results are shown below in Table 4. In Table 4,each of the joints are numbered 1 through 6, where joint 1 is the topjoint and joint 6 is the bottom joint when oriented vertically. Unlessotherwise noted, the number in the cells indicates the number ofsuccessful cycles before a break. An asterisk (“*”) next to a numberindicates that the joint was unbroken but that the test wasdiscontinued. The results are summarized in Table 4 below:

TABLE 4 Bond Durability Test Coupon Arrangement 1 6 Sample Top 2 3 4 5Bottom Sample 14 59* 59* 59  59 56 47 Sample 15 67* 67* 66  67 63 59Sample 16 64* 59  62  64  64* 63 Sample 17 49* 49* 42* 40 41 49 Sample18 61* 60  59  61 58  61* Sample 19 63* 63  63* 59 55 56 Sample 20 63 67* 59  67  67* 62 Sample 21 63  63* 49  54  63* 57 Sample 22 71* 59 71* 57 58 71 Sample 23 69* 65  69* 66 64 69

The exemplary corrosion resistant substrates which were subjected tothermal modification according to the present disclosure demonstratedexcellent bond durability, with all but one sample (Sample 17) passingthe test.

Example 3: GDOES Depth Profiling

Several samples of a corrosion resistant substrate were preparedaccording to the disclosed methods using an AA7075 aluminum alloy totest the properties of the corrosion resistant substrate. Each of thesamples tested is shown in Table 5. Samples were prepared by etchingwith an acid and applying a varying titanium/zirconium pretreatment(Gardobond 4591 from Chemetall GmbH (Frankfurt, Germany)), as detailedin Table 5. Each sample was prepared at an initial F temper. Each samplewas thermally modified to adjust the temper, as indicated in Table 5.

TABLE 3 Intl. Pretreatment Thermal Final Sample ID Temper Acid Etch FilmModification Temper Sample 25 F 0.2 g/m², Ti: 22 mg/m², 125° C. for T665° C., Zr: 20 mg/m², 24 hours 5 seconds 10 seconds 65° C. T6 Sample 26F 0.2 g/m², Ti: 17 mg/m², 125° C. for 50° C., Zr: 11 mg/m², 24 hours 1second 10 seconds 25° C.

To analyze the surface and depth profile, each sample was subjected toglow discharge optical emission spectrometry (GDOES). GDOES gives thequantitative depth distribution of elements in the thin surface film ofeach sample. The results of the GDOES depth profiling are illustratedFIG. 1 , which shows the enrichment of copper and silicon on the surfaceof the samples. With regard to copper, Samples 25 and 26 exhibitedsimilar profiles with the presence of copper enrichment after 12 secondsof sputtering. With regard to silicon, Sample 25 had higher yet thinnerenrichment of silicon than Sample 26, which may be due to the differencein the acid etching between the two samples.

1. A method of making a corrosion resistant substrate, the methodcomprising: producing a pretreatment film on a surface of a metalsubstrate to provide a pretreated metal substrate; and heating thepretreated metal substrate at a first temperature to provide thecorrosion resistant substrate, wherein the first temperature is greaterthan 300° C., and wherein the metal substrate and/or the pretreatedmetal substrate is in an F temper, a T4 temper, or a T6 temper.
 2. Themethod of claim 1, wherein the metal substrate comprises an aluminumalloy.
 3. The method of claim 2, wherein the metal substrate comprises a5xxx series aluminum alloy, a 6xxx series aluminum alloy, or a 7xxxseries aluminum alloy.
 4. (canceled)
 5. The method of claim 1, whereinthe pretreatment film comprises an oxide layer.
 6. The method of claim5, wherein the oxide layer comprises an aluminum oxide, a silicon oxide,a titanium oxide, a chromium oxide, a manganese oxide, a nickel oxide, ayttrium oxide, a zirconium oxide, a molybdenum oxide, or combinationsthereof.
 7. The method of claim 1, wherein producing the pretreatmentfilm comprises applying an inorganic pretreatment composition to thesurface of the metal substrate.
 8. The method of claim 1, whereinproducing the pretreatment film comprises anodizing the surface of themetal substrate.
 9. The method of claim 1, wherein producing thepretreatment film comprises flame hydrolyzing the surface of the metalsubstrate.
 10. The method of claim 1, wherein the first temperature isfrom 300° C. to 550° C.
 11. The method of claim 1, wherein the heatingcomprises heating the pretreated metal substrate at the firsttemperature for less than 30 minutes.
 12. The method of claim 1, whereinthe heating further comprises heating the pretreated metal substrate ata second temperature.
 13. The method of claim 12, wherein the secondtemperature is lower than the first temperature.
 14. The method of claim12, wherein the second temperature is from 75° C. to 250° C.
 15. Themethod of claim 12, wherein the heating comprises heating the pretreatedmetal substrate at the second temperature from 1 hour to 48 hours. 16.The method of claim 1, wherein the metal substrate is a continuous coil.17. A corrosion resistant coil comprising: an aluminum alloy continuouscoil, wherein a surface of the aluminum alloy continuous coil comprisesan inorganic pretreatment film, and wherein the aluminum alloycontinuous coil is in an F temper, a T4 temper, or a T6 temper.
 18. Themethod of claim 17, wherein the aluminum alloy continuous coil comprisesa 5xxx series aluminum alloy, a 6xxx series aluminum alloy, or a 7xxxseries aluminum alloy.
 19. The corrosion resistant coil of claim 17,wherein the inorganic pretreatment film comprises an oxide layer. 20.The corrosion resistant coil of claim 19, wherein the oxide layercomprises an aluminum oxide, a silicon oxide, a titanium oxide, achromium oxide, a manganese oxide, a nickel oxide, a yttrium oxide, azirconium oxide, a molybdenum oxide, or combinations thereof.
 21. Amethod of making a corrosion resistant substrate, the method comprising:producing a pretreatment film on a surface of a metal substrate toprovide a pretreated metal substrate; and heating the pretreated metalsubstrate at a first temperature to provide the corrosion resistantsubstrate, wherein the metal substrate and/or the pretreated metalsubstrate is in an F temper, and wherein the corrosion resistantsubstrate is in a T5 temper, a T6 temper, a T61 temper, a T7 temper, T8xtemper, or a T9 temper.